Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$44.40	8.765%	$48.2917	$48.29	$48.30	$48.30
Purchase #2	$86.65	4.422%	$90.4817	$90.48	$90.50	$90.50
Purchase #3	$241.61	5.717%	$255.4228	$255.42	$255.40	$255.40
Purchase #4	$159.96	8.345%	$173.3087	$173.31	$173.30	$173.30
Purchase #5	$162.60	9.251%	$177.6421	$177.64	$177.65	$177.60
Purchase #6	$46.98	6.766%	$50.1587	$50.16	$50.15	$50.20
Purchase #7	$234.28	13.430%	$265.7438	$265.74	$265.75	$265.70
7 purchase totals =	$976.48		$1,061.0495	$1,061.04	$1,061.05	$1,061.00